default_values (#340)

* do not create Variant with value None when they are supported by protocol

* add get_default_value to uatypes. This will be usefull at several places like opcuamodeler

* set correct default value in high level type creation method

opcua/common/manage_nodes.py

@@ -357,10 +357,11 @@ def _create_method(parent, nodeid, qname, callback, inputs, outputs):
 def _vtype_to_argument(vtype):
     if isinstance(vtype, ua.Argument):
         return vtype
-
     arg = ua.Argument()
-    v = ua.Variant(None, vtype)
-    arg.DataType = _guess_datatype(v)
+    if isinstance(vtype, ua.VariantType):
+        arg.DataType = ua.NodeId(vtype.value)
+    else:
+        arg.DataType = ua.NodeId(vtype)
     return arg
 
 

opcua/server/server.py

@@ -381,16 +381,16 @@ class Server(object):
             base_t = Node(self.iserver.isession, ua.NodeId(basetype))
 
         custom_t = base_t.add_object_type(idx, name)
-        for property in properties:
+        for prop in properties:
             datatype = None
-            if len(property) > 2:
-                datatype = property[2]
-            custom_t.add_property(idx, property[0], None, varianttype=property[1], datatype=datatype)
+            if len(prop) > 2:
+                datatype = prop[2]
+            custom_t.add_property(idx, prop[0], ua.get_default_value(prop[1]), varianttype=prop[1], datatype=datatype)
         for variable in variables:
             datatype = None
             if len(variable) > 2:
                 datatype = variable[2]
-            custom_t.add_variable(idx, variable[0], None, varianttype=variable[1], datatype=datatype)
+            custom_t.add_variable(idx, variable[0], ua.get_default_value(variable[1]), varianttype=variable[1], datatype=datatype)
         for method in methods:
             custom_t.add_method(idx, method[0], method[1], method[2], method[3])
 

opcua/ua/uatypes.py

@@ -9,8 +9,6 @@ import os
 import uuid
 import re
 import itertools
-if sys.version_info.major > 2:
-    unicode = str
 
 from opcua.ua import ua_binary as uabin
 from opcua.ua import status_codes
@@ -20,6 +18,8 @@ from opcua.ua.uaerrors import UaStatusCodeError
 from opcua.ua.uaerrors import UaStringParsingError
 
 
+if sys.version_info.major > 2:
+    unicode = str
 def get_win_epoch():
     return uabin.win_epoch_to_datetime(0)
 
@@ -27,8 +27,9 @@ def get_win_epoch():
 class _FrozenClass(object):
 
     """
-    make it impossible to add members to a class.
-    This is a hack since I found out that most bugs are due to misspelling a variable in protocol
+    Make it impossible to add members to a class.
+    Not pythonic at all but we found out it prevents many many
+    bugs in use of protocol structures
     """
     _freeze = False
 
@@ -38,6 +39,7 @@ class _FrozenClass(object):
                 key, self.__class__.__name__, self.__dict__.keys()))
         object.__setattr__(self, key, value)
 
+
 if "PYOPCUA_NO_TYPO_CHECK" in os.environ:
     # typo check is cpu consuming, but it will make debug easy.
     # if typo check is not need (in production), please set env PYOPCUA_NO_TYPO_CHECK.
@@ -750,6 +752,11 @@ class Variant(FrozenClass):
             self.VariantType = value.VariantType
         if self.VariantType is None:
             self.VariantType = self._guess_type(self.Value)
+        if self.Value is None and self.VariantType not in (
+                VariantType.Null,
+                VariantType.String,
+                VariantType.DateTime):
+            raise UaError("Variant of type {} cannot have value None".format(self.VariantType))
         if self.Dimensions is None and type(self.Value) in (list, tuple):
             dims = get_shape(self.Value)
             if len(dims) > 1:
@@ -1032,3 +1039,47 @@ def datatype_to_varianttype(int_type):
         return VariantType(int_type)
     else:
         return VariantTypeCustom(int_type)
+
+
+def get_default_value(vtype):
+    """
+    Given a variant type return default value for this type
+    """
+    if vtype == VariantType.Null:
+        return None
+    elif vtype == VariantType.Boolean:
+        return False
+    elif vtype in (VariantType.SByte, VariantType.Byte, VariantType.ByteString):
+        return b""
+    elif 4 <= vtype.value <= 9:
+        return 0
+    elif vtype in (VariantType.Float, VariantType.Double):
+        return 0.0
+    elif vtype == VariantType.String:
+        return None  # a string can be null
+    elif vtype == VariantType.DateTime:
+        return datetime.now()
+    elif vtype == VariantType.Guid:
+        return uuid.uuid4()
+    elif vtype == VariantType.XmlElement:
+        return None  #Not sure this is correct
+    elif vtype == VariantType.NodeId:
+        return NodeId()
+    elif vtype == VariantType.ExpandedNodeId:
+        return NodeId()
+    elif vtype == VariantType.StatusCode:
+        return StatusCode()
+    elif vtype == VariantType.QualifiedName:
+        return QualifiedName()
+    elif vtype == VariantType.LocalizedText:
+        return LocalizedText()
+    elif vtype == VariantType.ExtensionObject:
+        return ExtensionObject()
+    elif vtype == VariantType.DataValue:
+        return DataValue()
+    elif vtype == VariantType.Variant:
+        return Variant()
+    else:
+        raise RuntimeError("function take a uatype as argument, got:", vtype)
+
+

tests/tests_server.py

@@ -320,7 +320,7 @@ class TestServer(unittest.TestCase, CommonTests, SubscriptionTests, XmlTests):
 
         ev = opcua.common.events.get_event_obj_from_type_node(etype)
         check_custom_event(self, ev, etype)
-        self.assertEqual(ev.PropertyNum, None)
+        self.assertEqual(ev.PropertyNum, 0)
         self.assertEqual(ev.PropertyString, None)
 
     def test_eventgenerator_customEvent(self):
@@ -330,7 +330,7 @@ class TestServer(unittest.TestCase, CommonTests, SubscriptionTests, XmlTests):
         check_eventgenerator_CustomEvent(self, evgen, etype)
         check_eventgenerator_SourceServer(self, evgen)
 
-        self.assertEqual(evgen.event.PropertyNum, None)
+        self.assertEqual(evgen.event.PropertyNum, 0)
         self.assertEqual(evgen.event.PropertyString, None)
 
     def test_eventgenerator_double_customEvent(self):
@@ -343,12 +343,12 @@ class TestServer(unittest.TestCase, CommonTests, SubscriptionTests, XmlTests):
         check_eventgenerator_SourceServer(self, evgen)
 
         # Properties from MyEvent1
-        self.assertEqual(evgen.event.PropertyNum, None)
+        self.assertEqual(evgen.event.PropertyNum, 0)
         self.assertEqual(evgen.event.PropertyString, None)
 
          # Properties from MyEvent2
-        self.assertEqual(evgen.event.PropertyBool, None)
-        self.assertEqual(evgen.event.PropertyInt, None)
+        self.assertEqual(evgen.event.PropertyBool, False)
+        self.assertEqual(evgen.event.PropertyInt, 0)
 
     def test_eventgenerator_customEvent_MyObject(self):
         objects = self.opc.get_objects_node()
@@ -359,7 +359,7 @@ class TestServer(unittest.TestCase, CommonTests, SubscriptionTests, XmlTests):
         check_eventgenerator_CustomEvent(self, evgen, etype)
         check_event_generator_object(self, evgen, o)
 
-        self.assertEqual(evgen.event.PropertyNum, None)
+        self.assertEqual(evgen.event.PropertyNum, 0)
         self.assertEqual(evgen.event.PropertyString, None)
 
     def test_context_manager(self):